The present invention relates to pumping apparatuses, and more particularly to revolving propeller units for axial flow propeller pumps driven by a hydraulic motor as well as conventional extended shaft pumps.
Axial flow pumps are widely used in the industry for storm drainage, pumping transfer, irrigation, flood control, construction de-watering and the like. Axial flow pumps are often utilized in submersible installations, wherein the main drive unit is positioned on the surface, while the pump itself, having a propeller unit connected through a short internal shaft to a sealed hydraulic motor is submerged under water. The main power drive unit produces high pressure oil which is conduited down to the hydraulic motor of the submerged unit, so as to rotate the pump propeller with a certain number of revolutions per minute. The required revolutions of the propeller directly depend on the amount of load on the propeller and the head, that is the amount of water pumped by the submerged unit. However, such arrangement suffers from a certain disadvantage, when the amount of pressure delivered to the submersed unit is not proportional to the amount of load on the propeller, at which time the main driving unit operates at its full capacity when there is no need for it. For example, such situation may occur when a high power unit is positioned on the surface of a spillway to drain a small amount of water from one water body across the spillway to the other water body. The high powered unit continues to operate, as if it were driving an axial flow pump designed to pump a great amount of water, when there is actually no need for such high pressure to be delivered to the submerged unit. Apparently, such situation wears out the main driving unit and the increased revolutions of the shaft may damage and destroy the safety valve on the hydraulic oil supply. An acceptable practice in such cases was to reduce the revolutions of the main driving motor, allowing the relief valve to relieve the excessive pressure and detain the revolutions of the main driving unit on the same level but most of the oil that is being driven by the hydraulic unit is wasted just circulating back to the unit, causing an increased thermal build-up.
The present invention contemplates provision of a propeller unit which can vary the pitch of the propeller, depending on the amount of load on the propeller in any particular situation automatically, without the need for manual adjustment.